1. Field of the Invention
The present invention relates to a computer with a keyboard unit including a pointing device.
2. Description of the Related Art
Various types of portable personal computer, such as a notebook computer and a laptop computer, which can be carried easily and operated by a battery, have recently been developed. These personal computers employ built-in pointing device such a track ball, a pointing stick, and a touch pad.
Since the pointing stick can be arranged in a keyboard unit, the area of the pointing device occupied in the computer can be reduced greatly, as compared with the case of a personal computer equipped with a track ball and a touch pad. The pointing stick is therefore effective in serving as a pointing device of small-sized personal computers, especially A4-sized and B5-sized computers.
However, in a conventional personal computer, though a pointing stick is arranged in a keyboard, the pointing stick and keyboard unit are connected to two separate connectors mounted on a system board through cables, thus causing a problem wherein the mounting efficiency is lowered, the cost is increased, and the assembly process is complicated.
Since a power supply for supplying power to the built-in pointing device, differs from that of a pointing device control IC mounted on the system board, there occurs a problem in which the control IC erroneously detects a signal supplied from the built-in pointing device.
In other words, since a number of electric components are mounted on the system board, their operation states may cause noise in the power supply of the control IC and thus the detection level of the control IC is likely to vary. If, in this case, there occur variations in relationship between the signal level of the built-in pointing device and the detection level of the control IC, the control IC erroneously detects the signal from the built-in pointing device, resulting in a drawback wherein a cursor moves freely without operating the built-in pointing device and software malfunctions.
Conventionally, since the keyboard unit and pointing stick are connected to the two connectors, which are mounted on the system board, through the cables, respectively, the mounting efficiency is lowered accordingly. Since, furthermore, the power supply for supplying power to the built-in pointing device, differs from that of the built-in pointing device control IC mounted on the system board, the control IC is likely to erroneously detect a signal from the built-in pointing device when noise or the like occurs in the power supply.
In the conventional computer described above, a mouse interface of a keyboard controller is employed by the control IC. To use an external mouse, therefore, it should be connected to the mouse interface of the keyboard controller through the control IC; however, in this case, a usable mouse is limited to one type supported by the control IC.